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Zhejiang Huahai Pharma received CFDA approval to produce efavirenz, an oral non-nucleoside reverse transcriptase inhibitor (NNRTI) used to control the symptoms of AIDS. Huahai is the first China drugmaker approved to make the drug. Huahai produced efavirenz API for Merck, which marketed the drug under the name Stocrin

Efavirenz is also used in combination with other antiretroviral agents as part of an expanded postexposure prophylaxis regimen to reduce the risk of HIV infection in people exposed to a significant risk (e.g. needlestick injuries, certain types of unprotected sex etc.).

The usual adult dose is 600 mg once a day. It is usually taken on an empty stomach at bedtime to reduce neurological and psychiatric adverse effects.

Merck synthesis of Efavirenz

History

Efavirenz was approved by the FDA on September 21, 1998, making it the 14th approved antiretroviral drug.

Efavirenz is a non-nucleoside reverse trancriptase inhibitor being studied clinically for use in the treatment of HIV infections and AIDS.

Efavirenz chemically known as (-) 6-Chloro-4-cyclopropylethynyl-4-trifluoromethyl- 1 , 4- dihydro-2H-3, 1-benzoxa zin-2-one, is a highly potent non-nucleoside reverse transcriptase inhibitor (NNRTI).A number of compounds are effective in the treatment of the human immunodeficiency virus (HIV) which is the retrovirus that causes progressive destruction of the human immune system. Effective treatment through inhibition of HIV reverse transcriptase is known for non- nucleoside based inhibitors. Benzoxazinones have been found to be useful non-nucleoside based inhibitors of HIV reverse transcriptase.(-) β-chloro^-cyclopropylethynyM-trifluoromethyl-l ,4-dihydro-2H-3,l -ben zoxazin-2-one (Efavirenz) is efficacious against HIV reverse transcriptase resistance. Due to the importance of (-)6-chloro-4-cyclopropylethynyl-4-trifluoromethyl-l,4-dihydro-2H-3,l-ben zoxazin-2- one, economical and efficient synthetic processes for its production needs to be developed.The product patent US5519021. discloses the preparation of Efavirenz, in Example-6, column-29, involving cyclisation of racemic mixture of 2-(2-amino-5-chlorophenyl)-4- cyclopropyl-l,l,l-trifluoro-3-butyn-2-ol using l ,l ‘-carbonyldiimidazole as carbonyl delivering agent to give racemic Efavirenz. Further, resolution of the racemic Efavirenz is carried out using (-) camphanic acid chloride to yield optically pure Efavirenz. However, research article published in the Drugs of the future, 1998, 23(2), 133-141 discloses process for manufacture of optically pure Efavirenz. The process involves cyclisation of racemic 2-(2-amino-5-chlorophenyl)-4-cyclopropyl-l, 1, l-trifluoro-3-butyn-2- ol using 1, 1-carbonyldiimidazole as carbonyl delivering agent to give racemic Efavirenz and further resolution by (-) camphanic acid chloride.Similarly research article published in Synthesis 2000, No. 4, 479-495 discloses stereoselective synthesis of Efavirenz (95%yield, 99.5%ee), as shown below

Even though many prior art processes report method for the preparation of Efavirenz, each process has some limitations with respect to yield, purity, plant feasibility etc. Hence in view of the commercial importance of Efavirenz there remains need for an improved process.

US 6 028 237 discloses a process for the manufacture of optically pure Efavirenz.

The synthesis of efavirenz and structurally similar reverse transcriptase inhibitors are disclosed in US Patents 5,519,021, 5,663,169, 5,665,720 and the corresponding PCT International Patent Application WO 95/20389, which published on August 3, 1995. Additionally, the asymmetric synthesis of an enantiomeric benzoxazinone by a highly enantioselective acetylide addition and cyclization sequence has been described by Thompson, et al., Tetrahedron Letters 1995, 36, 8937-8940, as well as the PCT publication, WO 96/37457, which published on November 28, 1996.

Additionally, several applications have been filed which disclose various aspects of the synthesis of(-)-6-chloro-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1-benzoxazin-2-one including: 1) a process for making the chiral alcohol, U.S.S.N. 60/035,462, filed 14 January 1997; 2) the chiral additive, U.S.S.N. 60/034,926, filed 10 January 1997; 3) the cyclization reaction, U.S.S.N. 60/037,059, filed 12 February 1997; and the anti-solvent crystallization procedure, U.S.S.N. 60/037,385 filed 5 February 1997 and U.S.S.N. 60/042,807 filed 8 April 1997.

Efavirenz has been obtained by two related ways: 1) The acylation of 4-chloroaniline (I) with pivaloyl chloride (II) by means of Na2CO3 in toluene gives the expected anilide (III), which is acylated with ethyl trifluoroacetate by means of butyllithium in THF yielding, after hydrolysis with HCl, 2′-amino-5′-chloro-2,2,2-trifluoroacetophenone (IV). The benzylation of (IV) with 4-methoxybenzyl chloride (V) in basic alumina affords the protected acetophenone (VI), which is regioselectively condensed with cyclopropylacetylene (VII) [obtained by cyclization of 5-chloro-1-pentyne (VIII) by means of butyllithium in cyclohexane] by means of butyllithium in THF in the presence of (1R,2S)-1-phenyl-2-(1-pyrrolidinyl)-1-propanol (IX) giving the (S)-isomer of the tertiary alcohol (X) exclusively. The cyclization of (X) with phosgene and triethylamine or K2CO3 in toluene/THF yields the benzoxazinone (XI), which is finally deprotected with ceric ammonium nitrate in acetonitrile/water. 2) The condensation of 2′-amino-5′-chloro-2,2,2-trifluoroacetophenone (IV) with cyclopropylacetylene (VIII) by means of butyllithium or ethylmagnesium bromide in THF gives (?-2-(2-amino-5-chlorophenyl)-4-cyclopropyl-1,1,1-trifluoro-3-butyn-2-ol (XII). The cyclization of (XII) with carbonyldiimidazole (XIII) in hot THF yields the racemic benzoxazinone (XIV). Compound (XIV) is submitted to optical resolution by condensation with (S)-(-)-camphanoyl chloride by means of dimethylaminopyridine (DMAP) in dichloromethane to give the acyl derivative (XVI) as a diastereomeric mixture that is resolved by crystallization and finally decomposed with HCl in ethanol or butanol.

Corley, E.G.; Thompson, A.S.; Huntington, M.F.; Grabowski, E.J.J.; Use of an ephedrine alkoxide to mediate enantioselective addition of an acetylide to a prochiral ketone: Asymmetric synthesis of the reverse transcriptase inhibitor L-743,726.

Tetrahedron Lett1995,36,(49):8937-40

EP 1332757 A1

Clips

When a commercial market already exists for the RMs used in synthesizing an API, their cost can be rather modest. When RMs used in synthesizing an API have no other commercial use, however, they can contribute very substantially to API cost. With a continued growth of volume demand, improved chemistry and competition from multiple suppliers, however, the cost of API RMs can greatly decrease over time. The inhibitor of HIV-1 RT, EFV, provides an illustration of this situation. Cyclopropylacetylene (CPA) is an RM for the synthesis of EFV (Figure 4). During clinical trials, when the demand for CPA was only a few metric tons, this material was produced at a price of USD800–1,350/kg. When the drug was first approved in 1998, and demand for CPA was about 50 metric tons per year, the price of CPA had fallen to USD350/kg. Today, with global demand for EFV at greater than 1,000 metric tons/year, CPA can be purchased for about USD50–60/kg. In the earliest stages of production, nearly 1 kg of CPA was needed to produce a kilogram of EFV. Current production processes are more efficient; roughly 3 kg of EFV is now produced for each 1 kg of CPA used. From this it can be roughly estimated that the contribution of CPA to the cost of EFV API production has fallen from as high as USD425/kg to about USD17–20/kg today.

The most recent chemistry for asymmetric alkynylation of manufacturing EFV uses inexpensive, safe reagents and processing at ambient temperature to reach EFV pricing that would have been thought impossible when the drug was launched by Dupont Pharmaceuticals in 1998

FPPs for adult ART are usually capsules or tablets. A general rule-of-thumb is that an FPP as a conventional, solid oral dosage formulation costs about 33–40% more than the corresponding API in a competitive market. It has been widely quoted, conversely, that APIs contribute about 60–80% of the cost of an FPP. The API contribution to FPP cost increases with the complexity of synthesis and API cost per kilogram. Although marketing is a substantial incremental cost for originator pharmaceutical companies, generic producers do not incur high marketing costs for ART.

illustrates the great effect of new routes of synthesis on API costs. The manufacturing cost of route 1 for the launch of EFV in 1998 was about USD1,800/kg [31,41]. EFV API was priced at about USD1,100/kg for the first generic launch in 2005. At this time the price of CPA was about USD250/kg. The best prices for EFV API in 2012–2013 are USD120–130/kg prepared under GMP. This drastic 89% reduction in generic API pricing is due in part to volume demand – the LMIC use of generic EFV in 2012 exceeded 750 metric tons and was estimated to exceed 900 metric tons in 2013. Reductions in the cost of RMs have also had a significant effect. More efficient processes for producing the final intermediate SD 573, have contributed the largest part to price reductions [42]. The route 1 synthesis requires five steps while routes 2 through 4 require only two steps from the same starting materials for the commercial production of EFV.

Chemical properties

Efavirenz is chemically described as (S)-6-chloro-(cyclopropylethynyl)-1,4-dihydro-4-(trifluoromethyl)-2H-3,1-benzoxazin-2-one. Its empirical formula is C14H9ClF3NO2. Efavirenz is a white to slightly pink crystalline powder with a molecular mass of 315.68 g/mol. It is practically insoluble in water (<10 µg/mL).

History

Efavirenz was approved by the FDA on September 21, 1998, making it the 14th approved antiretroviral drug.

Society and culture

Pricing information

A one-month supply of 600 mg tablets cost approximately $550 in April 2008.[16] Merck provides efavirenz in certain developing countries at cost, currently about $0.65 per day.[17] Some emerging countries have opted to purchase Indian generics[18] such as Efavir by Cipla Ltd.[19] In Thailand, one month supply of efavirenz + truvada, as of June 2012, costs THB 2900 ($90), there’s also a social program for poorer patients who can’t afford even this price. In South Africa, a license has been granted to generics giant Aspen Pharmacare to manufacture, and distribute to Sub-Saharan Africa, a cost-effective antiretroviral drug.[20]

PATENT

To a solution of trifluoroethanol and (IR, 2S)-N-pyrrolidinyl norephedrine in THF (9 L) under nitrogen is added a solution of diethylzinc in hexane at 0 °C slowly enough to keep the temperature below 30 °C. The mixture is stirred at room temperature for 0.5 ~ 1 h. In another dry flask a solution of chloromagnesium cyclopropyl acetylide is prepared as follows: To neat cyclopropyl acetylene at 0 °C is added a solution of rc-butylmagnesium chloride slowly enough to keep the internal temperature < 30 °C. The solution is stirred at 0 °C for ~ 40 min and transfered to the zinc reagent via cannula with 0.36 L of THF as a wash. The mixture is cooled to -10 °C and ketoaniline la is added. The mixture is stirred at -2 to -8 °C for 35 h, warmed to room temperature, stirred for 3 h, and quenched with 30% potassium carbonate over 1.5 h. The mixture is stirred for 4 h and the solid is removed by filtration and washed with THF (2 cake volume). The wet solid still contains -18 wt% of pyrrolidinyl norephedrine and is saved for further study. The filtrate and wash are combined and treated with 30% citric acid. The two layers are separated. The organic layer is washed with water (1.5 L). The combined aqueous layers are extracted with 2.5 L of toluene and saved for norephedrine recovery. The toluene extract is combined with the organic solution and is concentrated to ~ 2.5 L. Toluene is continuously feeded and distilled till THF is not detectable by GC. The final volume is controlled at 3.9 L. Heptane (5.2 L) is added over 1 h. The slurry is cooled to 0 °C, aged for 1 h, and filtered. The solid is washed with heptane (2 cake volume) and dried to give 1.234 Kg (95.2% yield) of amino alcohol 3 as a white crystalline. The material is 99.8 A% pure and 99.3% ee.

EXAMPLE 2

To a three necked round bottom flask, equipped with a mechanical stirrer, nitrogen line, and thermocouple, was charged the solid amino alcohol 3, MTBE (500 L), and aqueous KHCO3 (45 g in 654 mL H2O). Solid 4-nitrophenyl chloroformate was added, in 4 batches, at 25°C. During the addition the solution pH was monitored. The pH was maintained between 8.5 and 4 during the reaction and ended up at 8.0. The mixture was stirred at 20-25°C for two hours. Aqueous KOH (2N) was added over 20 minutes, until the pH of the aqueous layer reached 11.0.

The layers were separated and 500 mL brine was added to the MTBE layer. 0.1 N Acetic acid was added until the pH was 6-7. The layers were separated and the organic phase was washed with brine (500 mL). At this point the mixture was solvent switched to EtOH/IPA and crystallized as recited in Examples 5 and 6.

EXAMPLE 3

To a three necked round bottom flask, equipped with a mechanical stirrer, nitrogen line, and thermocouple, was charged the solid amino alcohol 3a, toulene (500 mL), and aqueous KHCO3 (86.5 g in 500 L H2O). Phosgene solution in toulene was added at 25°C, and the mixture was stirred at 20-25°C for two hours.

The layers were separated and the organic phase was washed with brine (500 mL). At this point the mixture was solvent switched to EtOH/IPA and crystallized as recited in Examples 5 and 6.

EXAMPLE 4

To a three necked round bottom flask, equipped with a mechanical stirrer, nitrogen line, and thermocouple, was charged the solid amino alcohol 3a, MTBE (500 mL), and aqueous KHCO3 (86.5 g in 500 mL H2O). Phosgene gas was slowly passed into the solution at 25°C, until the reaction was complete.

The layers were separated and the organic phase was washed with brine (500 mL). At this point the mixture was solvent switched to EtOH/IPA and crystallized as recited in Examples 5 and 6.

EXAMPLE 5

Crystallization of efavirenz from 30% 2-Propanol in Water using a ratio of 15 ml solvent per gram efavirenz Using Controlled Anti-Solvent Addition on a 400 g Scale.

400 g. of efavirenz starting material is dissolved in 1.8 L of 2- propanol. The solution is filtered to remove extraneous matter. 1.95 L of deionized (DI) water is added to the solution over 30 to 60 minutes. 10 g. to 20 g. of efavirenz seed (Form II wetcake) is added to the solution. The seed bed is aged for 1 hour. The use of Intermig agitators is preferred to mix the slurry. If required (by the presence of extremely long crystals or a thick slurry), the slurry is wet-milled for 15 – 60 seconds. 2.25 L of DI water is added to the slurry over 4 to 6 hours. If required (by the presence of extremely long crystals or a thick slurry), the slurry is wet- milled for 15 – 60 seconds during the addition. The slurry is aged for 2 to 16 hours until the product concentration in the supernatant remains constant. The slurry is filtered to isolate a crystalline wet cake. The wet cake is washed with 1 to 2 bed volumes of 30 % 2-propanol in water and then twice with 1 bed volume of DI water each. The washed wet cake is dried under vacuum at 50°C.

EXAMPLE 6

Crystallization of efavirenz from 30% 2-Propanol in Water using a ratio of 15 ml solvent per gram efavirenz Using a Semi-Continuous Process on a 400 g Scale.

400 g. of efavirenz starting material is dissolved in 1.8 L of 2- propanol. A heel slurry is produced by mixing 20 g. of Form II efavirenz in 0.3 L of 30 % (v/v) 2-propanol in water or retaining part of a slurry froma previous crystallization in the crystallizer. The dissolved batch and 4.2 L of DI water are simultaneously charged to the heel slurry at constant rates over 6 hours to maintain a constant solvent composition in the crystallizer. Use of Intermig agitators during the crystallization is preferred. During this addition the slurry is wet-milled when the crystal lengths become excessively long or the slurry becomes too thick. The slurry is aged for 2 to 16 hours until the product concentration in the supernatant remains constant. The slurry is filtered to isolate a crystalline wet cake. The wet cake is washed with 1 to 2 bed volumes of 30 % 2-propanol in water and then twice with 1 bed volume of DI water each. The washed wet cake is dried under vacuum at 50°C.

A solution of diethyl zinc in hexane was added to a solution of trifluoroethanol (429.5 g, 4.29’mol) and (IR, 2S)-N-pyrrolidinyl norephedrine (1.35 kg, 6.58 mol) in THF (9 L), under nitrogen, at 0 °C. The resulting mixture was stirred at room temperature for approx. 30 min. In another dry flask a solution of chloromagnesium- cyclopropylacetylide was prepared as follows. To a solution of n- butylmagnesium chloride in THF (2 M, 2.68 L, 5.37 mol) was added neat cyclopropylacetylene at 0 °C keeping the temperature < 25 °C. The solution was stirred at 0 °C for 1 ~ 2 h. The solution of chloromagnesiumcyclopropylacetylide was then warmed to room temperature and was transferred into the zinc reagent via cannula over 5 min followed by vessel rinse with 0.36 L of THF. The resulting mixture was aged at ~ 30 °C for 0.5 h and was then cooled to 20 °C. The ketoaniline 1 (1.00 kg, 4.47 mol) was added in one portion as a solid, and the resulting mixture was stirred at 20-28 °C for 3 h.

The reaction was quenched with 30% aq. potassium carbonate (1.2 L) and aged for 1 h. The solid waste was filtered and the cake was washed with THF (3 cake volumes). The filtrate and wash were combined and solvent switched to IP Ac.

The IPAc solution of product 3 and pyrrolidinyl norephedrine was washed with citric acid (3.5 L) and with water (1.5 L). The combined aqueous layers were extracted with IPAc (2 L) and saved for norephedrine recovery. To the combined organic layers was added

12N HC1 (405 mL, 4.88 mol), to form a thin slurry of the amino alcohol-

HC1 salt. The mixture was aged for 30 min at 25 °C and was then dried azeotropically. The slurry was aged at 25 °C for 30 min and filtered. The cake was washed with 2.5 L of IPAc and dried at 25 °C under vacuum/nitrogen for 24 h to give 1.76 kg of the wet HC1 salt.

The salt was dissolved in a mixture of MTBE (6 L) and aq Na2Cθ3 (1.18 kg in 6.25 L water). The layers were separated and the organic layer was washed with 1.25 L of water. The organic layer was then solvent switched into toluene.

Heptane (5 L) was added over 1 h at 25 °C. The slurry was cooled to 0 °C, aged for 1 h, and filtered. The solid was washed with heptane (2 cake volumes) and was dried to give 1.166 kg (90% overall yield) of amino alcohol 3 as a white crystalline solid. Norephedrine recovery

The aqueous solution was basified to pH13 using 50% aq NaOH, and extracted with heptane (2 L). The heptane solution was washed with water (1 L) and concentrated to remove residual IPAc and water. The final volume was adjusted to about 3 L. The heptane solution was cooled to -20 °C, aged for 2 h, and filtered. The solid was washed with cold heptane (1 cake volume) and dried to give 1.269 kg solid (94% recovery)

TLC388 (Lipotecan) is a potent Topoisomerase-1 inhibitor and it can disrupt both Sonic Hedgehog and HIF1-α pathways to overcome cancer drug resistance and inhibit angiogenesis induced by tumor hypoxia. This phase I first-in-human study of Lipotecan examined the MTD, safety, anti-tumor activity and pharmacokinetic profiles of TLC388 in patients with advanced incurable solid tumors.

Methods: Lipotecan was administered intravenously on day 1, 8 and 15 of a 28-day cycle. Patients underwent safety assessments regularly and tumor assessments every other cycle. Pharmacokinetic samples were drawn on days 1, 8 and 15 of cycles 1 and 2 for all treated patients.

China SFDA has granted fast track approval status to Taiwan Liposome company hepatic cancer drug Lipotecan, shortening the review period. The drug will enter Phase 2 clinical trials in China in the second half of this year. Lipotecan has been granted orphan drug status by US FDA and EU EMEA for the treatment of hepatocellular carcinoma (HCC)

Nexavar is the standard of care in first line advanced liver cancer patients. Lipotecan as a second-line treatment allows patients who have failed prior treatment with Nexavar to maintain a six month course of the disease without progressing

Lipotecan is a second generation camptothecin drug emphasize on modification on E-ring with a group which not only stabilizes the active site but also functions as a strong radio-sensitizer to overcome radio- and chemo-resistance that is frequently encountered in clinical therapies, enabling Lipotecan® to tailor at unmet needs.